The effect of glycosaminoglycans on amphibian limb regeneration will be studied by injecting them into newt limbs. Embryonic chick corneal eptithelium will be cultured on collagen substrata and incorporation of 3H-proline into collagen and 35S into glycosaminoglycan measured. The effects of extraneous agents, such as thyroxine and epidermal growth factor, will be studied. Immunohistochemistry is being done at the electron microscope level using labeled antibodies to localize fibronectin and various collagen types in embryonic chick tissues. Both scanning and transmission electron microscopes are being used and several labels are being tried, including ferritin and acrylate spheres.